This invention relates to the field of materials having a low dielectric constant, especially to such materials in the form of films containing a liquid crystal polymer ("LCP") suitable for use in the electronics industry.
In applications requiring electrical insulation, the effectiveness of a material as insulation is related to the dielectric constant and the thickness of the material. The dielectric constant is particularly crucial where increasing thickness is not a viable option, e.g., in electronic applications requiring thin film insulation layers. However, a material having a low dielectric constant may lack other important properties, such as chemical and temperature resistance, mechanical strength, and reasonable cost. To achieve the desired combination of properties, a material comprising a mixture of two or more components may be needed, for example, a relatively inexpensive low dielectric component and a higher performance component having the desired physical and chemical properties.
When a homogeneous mixture of dielectric elements or components is present, the dielectric constant of the multi-component material may be determined by averaging the dielectric constants of the components in proportion to the amount of each component present in the material.
Liquid crystal polymers generally exhibit good chemical, moisture and temperature resistance, and good mechanical strength, and can be formed into thin films that have a high degree of structural integrity. However, the cost and/or the dielectric constant of a film made solely of LCP may be too high for certain electronic applications.
Polytetrafluoroethylene ("PTFE") lacks the physical strength of an LCP, but has a lower dielectric constant and a greater chemical resistance.
Hollow glass spheres are inexpensive and generally have a low dielectric constant, depending on the size of the sphere and the wall thickness. Of course, to form films something must hold them together. However, when used in film-forming polymers, hollow glass provides good mechanical reinforcement and lowers the dielectric constant, cost, and weight of the material.